1. Field of the Invention
This invention relates to an analysis apparatus which analyzes elements on the basis of fluorescence obtained from plasma produced by the irradiation of laser light.
2. Description of the Related Art
One known analysis apparatus irradiates laser light onto an analysis object and determines the quantity of fluorescence produced by the irradiation of laser light, thereby making it possible to analyze the elements of the analysis object with no pretreatment in as short an analysis time as about 100 milliseconds, which enables real-time analysis (e.g., refer to (FIGS. 4 and 5 in page 6 of) Jpn. Pat. Appln. KOKAI Publication No. 2000-310596).
The analysis apparatus condenses laser light with a laser light condensing optical system and irradiates the condensed laser light onto the surface of an analysis object, thereby turning the elements at the surface of the analysis object into plasma. As soon as the irradiation of laser light has ended, the plasma starts to recombine, with the result that the constituent elements of the analysis object turn into excited-state atoms in several microseconds to several tens of microseconds. When the exited-state atoms transit to a lower level, fluorescence whose amount is proportional to the number of atoms is emitted at a wavelength peculiar to the atoms. Then, part of the fluorescence emitted from the analysis object is condensed by the fluorescence condensing optical system from the lateral direction of the laser light condensing optical system. The fluorescence is analyzed spectroscopically by a fluorescence measuring instrument, thereby analyzing the elements included in the substance that emitted the fluorescence.
Furthermore, the use of optical fiber for both of the transmission of laser light and the transmission of fluorescence improves the flexibility of analysis, which provides an analysis apparatus having superior characteristics to those of, for example, a fluorescence X-ray analysis apparatus. When laser light is transmitted through an optical fiber, the irradiation area (or analysis area) of laser light is limited, since transmittable laser light energy is limited because the optical fiber can be damaged if laser light energy to be transmitted is excessive, and since examination results have shown that an energy density of about 25 mJ/mm2 or more is required to produce plasma by the irradiation of laser light. However, the limitation of the laser light irradiation area provides the advantage of assuring the flexibility of analysis.
As described above, in the analysis apparatus, the use of optical fiber for both of the transmission of laser light and the transmission of fluorescence assures the flexibility of analysis. However, when fluorescence is condensed by the fluorescence condensing optical system from the lateral direction of the laser light condensing optical system and is transferred through an optical fiber, the surface of the analysis object must be so flat that the collection of fluorescence is not impeded. If the surface of the analysis object is irregular or has a curvature, the fluorescence condensing optical system that condenses fluorescence from the lateral direction of the laser light condensing optical system cannot condense fluorescence sufficiently, which might make analysis difficult.
It is, accordingly, an object of the present invention to provide an analysis apparatus which permits only a small decrease in the sensitivity due to the effect of the shape of an analysis object, enables the analysis accuracy to be improved, makes it possible to integrate the laser light condensing optical system and the fluorescence condensing optical system with each other to make the system more compact, and further enables the collection of fluorescence to be adjusted easily.